Tamper proof manifold



Aug- 1961 J. w. TAMPLEN ET AL 2,998,070

TAMPER PROOF MANIFOLD Filed Nov. 17, 1958 4 Sheets-Sheet 1 Kfi piiiil/il"R Q W5 Ahnna FIG-4 Arrow/5K5 Aug. 29, 1961 J. w. TAMPLEN ET AL2,998,070

TAMPER PROOF MANIFOLD Filed Nov 17, 1958 4 Sheets-Sheet s INVENTOR5 J46!(d. AMPLEA/ PH/Ll/P J. 5/25? Arrow/5K5 1961 J. w. TAMPLEN' ETAL'2,998,070

TAMPER PRdOF MANIFOLD Filed Nov. 17, 1958 4 Sheets-Sheet 4 INVENTORS.1746? (d. TflMPLE/V PH/lL/PZS/ZE? "United SW65 Pa ent- Filed Nov. 17,1958, Ser. No. 774,497 Claims. (Cl. 166-72) invention relates to meansfor automatically stopping fluid flow in an oil Well tubing string uponrupture of the tubing string or flow line above a safety valve made uptherein, or upon rupture of the means or accessory lines connecting themeans to either the flow line or safety valve.

This invention resulted from the necessity of finding a way of closingin an oil well were it to be sabotaged or otherwise caused to flowuncontrolled. This situation has recently occurred in certain foreigncountries where the wellheads of a number of wells were destroyed bydynamiting and other means and the wells flowed out of control forconsiderable lengths of time. In such cases tremendous quantities of oilare lost, and it is often extremely dangerous to close the well in. Somesuch wells have become exhausted before finally being closed in.

Numerous subsurface safety valves are currently available, which may beinstalled in a well tubing below the surface of the ground and whichwill stop fluid flow through the tubing upon rupture of the flow lineabove the wellhead. Their use alone, however, does not prevent the wellfrom being sabotaged, since they can be secured at the wellhead in theopen position and the flow line then sabotaged. This invention remediesthat deficiency in that the safety valve in the tubing string will beclosed if any of the following are ruptured: the surface flow line, themeans of this invention itself, the accessory line connecting the flowline and the means of this invention, or the accessory line connectingthe safety valve and the means of this invention.

Hence, a principal object of this invention is to provide means forclosing in a well upon rupture of the means, the accessory lines, theflow line, or tubing string at any point above the safety valve made upin the tubing string.

Another object is to provide means which, if tampered with or damaged inany material respect, will cause the safety valve in the tubing stringto close, thus closing in the well.

Another object is to provide such means which can be readily reset tocause the safety valve to open and thus to cause the well to resumeflowing.

Other objects and advantages will become apparent in the course of thefollowing detailed description.

In the drawings, forming a part of this application, and in which likeparts are designated by like reference numerals throughout the same,

FIG. 1 is a schematic representation of a system ermbodying theinvention showing the manifold connected to control the operation of thesubsurface safety valve in a well string.

FIGS. 2A and 2B are elevational sectional views of the manifold used inFIG. 1, with FIGS. 2A and 2B illustrating the left and right halves,respectively, of the manifold.

FIG. 3 is an elevational sectional view of the automatic reset pilotvalve used in the manifold.

FIG. 4 is an elevational sectional view of a reset tool for use with themanifold.

Referring now to the drawings, and specifically to FIG.

1 thereof, the tamper proof manifold 10 is to be used in conjunctionwith a conventional cased well 11 having a flow line 12 extending abovethe wellhead 13 and a tubing string 14. A safety valve 15 is made up inthe ice 2 I tubing string below the wellhead. The manifold has threaccessory conduits or outlets 16, 17 and 18, connecting it to the flowline 12, the safety valve 15, and the atmosphere, respectively. The pipecross 19 is made up in accessory line 17, with one outlet of the pipecross being attached to a pressure gage 21. The remaining out let of thepipe cross is connected to a valve 22 by means of which the manifold 10,line 17 and safety valve 15 are charged with hydraulic fluid underpressure from a suitable source 23. i

The subsurface safety valve 15 may be of any com: mon type wherein thevalve is operated to open position by suflicient fluid pressure inconduit 17 and where in the valve will close when the fluid pressurewithin conduit 17 decreases below a predetermined minimum. An example ofsuch a valve usable for the above purpose is that illustrated anddescribed at page 4124 of the Composite Catalog of Oil Field Equipmentand Services, 1957 edition, and which is schematically illustratedherein. When sufficient fluid pressure is exerted through conduit 17into piston chamber 25, the fluid pressure piston ac tuator 26 will beforced downwardly, rotating the ball valve 27 by the interaction of thehousing lugs 28 and ball valve grooves 29 so that the ball valve bore 30becomes aligned with the bore of the tubing string. When the pressure inpiston chamber 25 decreases, spring 31 forces piston 32 upwardly,rotating the ball valve to a position wherein the bore thereof istransverse to the bore of the tubing string to interrupt flow throughthe valve.

Referring now to the specific details of the manifold, as illustrated inFIGS. 2A and 2B, the manifold com prises an outer casing 35 formed froma tubular body member 36 sealed at its ends by unibzolt scraper trapcouplings 37 and 38,'welded thereto as at 39.

Unibolt scraper trap couplings are commonly used in the oil wellindustry and will be described herein only in so far as is necessary foran understanding of the presem invention. Such couplings are fullyillustrated at page 5137 (FIGS. 13b and 15c) of the Composite Catalog ofOil Field Equipment and Services, 1957 edition. 'Ilo seal the blankingplug 41 against the seal ring 42 (cartied by the hub 43), the blankingplug 41 is rotated with respect to nut 44 and hub 43 by tightening nuts45 on bolts 46 which join the arms 47 and 48 (mounted on the blankingplug 41 and nut 44, respectively). This causes the inclined lugs 49 and50 (on the blanking plug 41 and nut 44, respectively), to move relativeto one another so as to cam the blanking plug inwardly to compress theseal ring 42 against hub 43.

In the same way, the blanking plug 51 of the coupling 38 is sealed.

Connector 52 and fitting 53 are threadedly inserted in the blanking plug41. Connector 52 is connected by conduit 17 to the pipe cross fitting19, which in turn is connected to the valve 22, pressure gage 21, andsafety valve 15, as described hereinabove with reference to FIG. 1.Nipple 54 is welded to the internal surface of the blanking plug 41 at55. Fitting S3 communicates with the atmosphere through the opening 18within nut 44.

The blanking plug 51 at the right end of the outer casing 35 has twoports 57 and '58 communicating its interior and exterior surfaces.Connector 59, having an orifice fitting 60 threadedly inserted therein,threadedly engages port 57 in the blanking plug and is connected to theconduit 16 of FIG. 1. Nipple 61 is welded at 62 to the plug andcommunicates with port 58 therein, and is also connected to aconventional gate valve 63. The purpose of this gate valve is discussedhereinafter.

The inner casing 65 is contained completely within the outer casing 35to form an outer chamber A therebetween. An inner chamber B is formedwithin the inner casing 65. The left end of the inner casing is sealedby engagement of end-sub 66 therewith and O-ring 67 therebetween. Theleft end of the inner casing is positioned within chamber A by connector68 which at one end is .threadedly insertedin the end-sub and maintainedin this position by lock nut 69 and. at its other end is positionednipple 54 by pin 70. Connector ports 71 provide communication betweenchamber A and the connector passageway 72. Fitting 73, threadedlyinserted in end-sub passageway 74, and tubing 75, connected to fittings73 and 53, provide communication between chamber B and the atmosphere. 7

, The rig-ht end of the inner casing 65 is supported within and spacedfrom the outer casing by a plurality of legs 76 welded thereto. This endof the inner casing is sealed by the engagement of the housing member 77of pilot valve 78 therewith and the engagement of the piston cap 79 withthe housing member 77. Fitting 80 is threadedly inserted in passageway81 and by conduit 82 communiand .O-ring 89 therebetween, is disposedwithin the plunger guide and is maintained in this position betweenshoulders 90 and. 91. Nipple 92 is threadedly made up between seatretainer 85 and a pressure accumulator 93 to provide communicationbetween passageway 94 in the 7 seat retainer and a variable capacityreservoir 95 in the accumulator. Prior to being disposed in chamber B,the accumulator 93 is charged with gas through valve 96 to provideconstant pressure on piston 97 therein, whichin turn provides a constantpressure on the fluid in the reservoir 95 on the other side of thepiston and in the passageway 94. Elbow 98 is threadedly inserted in theseat retainer 85 and communicates throughconduit 99,.fittings 100,conduit 101, and fitting 102 to connector 52. Thus communication isprovided'between passageway 94 in the r seat retainer and the safetyvalve 15 made up in the well tubing string, as shown in FIG. 1. g

Piston 103 is disposed within the pilot valve 78. A piston chamber C isthus formed between the piston and the plunger guide 84 and pistonchamber D between the piston and piston cap 79. Chamber D communicateswith passageways 104 and 81. 'Passageway 104 is sealed by piston holddown'member 106, which extends through nipple 61 into gate valve 63. O-ring 107, disposed about the piston hold down, seals passageway 104.While the piston hold down can be forced to t'neleft to engage piston103 and thus enlarge chamber D, its displacement .to the right islimited by shoulder 108,

Chamber C communicates with. chamber B through passageways 109 and 110,and also through passageway 111. Plunger, or relief valve hold downmember, 112 is disposed within passageway 109 and abuts at one endpiston 103 and at its other end the relief ball valve113. The ball is ofthe proper diameter to seat againstthe .seat assembly 87, 88 and 89,thus disrupting cornmunication between passageway 94 and passageway 110.If,

however, fluid pressure in passageway 94 exerts a force on ball 113greater than the pressure in chamber D exerts on piston 103, the ballwill be displaced to the right, and the fiuid pressure inpassageway94'will be relieved into chamber B through passageway 110.

It is to be noted that the area of ball 113 exposed open to passageway94 is much less than the area of piston T103 facing chamber D.Therefore, a unit pressure within chamber D considerably smaller thanthat within *cham'oer94 will cause ball 113 to remain seated.

It is also to be noted that the ball 113 can be reseated by opening gatevalve '63, forcing piston hold down 106 to the left, and thereby forcingpiston 103 and plunger -112 to the left against the ball.

The device for performingthis last function is shown in FIG.-4,Iand.comprises ia-prong member 115 threadedly 4 engaged intermediateits ends to body member 116 and sealed thereto by O-ring 117. The bodymember 116 has external threads 118 thereon enabling it to be threadedlyinserted into the gate valve 63. Rotation of the prong member by handle119 will cause the prong member to move to the left and force againstthe piston hold down 106.

Referring now to the details of FIG. 3, it is seen that diaphragmhousing120 and reset pilot housing 121 are securely connected toone'another and are supported in chamber B by fitting 122, which isconnected in passageway 123 of the endssub 66, and in the diaphragmhousing 120. Fitting 122 also provides communication between chamber ,Fof the diaphragm housing and passageway 123 so that chambers A and Pwill be at the same fluid pressure. Diaphragm 124 provides apressure-tight seal. between chamber F and chamber E. Due to thepassageway 125, chamber E is at the same pressure as that within resetpilot housing 121, which is maintained at atmospheric pressure by meansof ports 126.

Reset pilot valve is fixedly secured to the reset pilot housing in theposition shown in FIG. 3. Conduit 131 leading from fittings 132, end-subpassage 133 and fitting .83, communicates through fitting 134 withpassageway 135 in pilot valve 130. Also, end-sub passage 136 and conduit137 place chamber A in fluid communication with passage 138 of pilotvalve 130. Plunger seat 139 is disposed within and threadedly connectedto reset pilot valve 130. Plunger 140is slidably disposed within the.plunger seat. With thesurfaces between the plunger {seat 139 and thereset pilot valve s'ealed by O-rings 141, 7 142 and 143, and thosebetween the plunger and plunger seat sealed by O-rings 144, 145-and.146, passageways 135 and 138 are sealed from one another when theplunger is in the position shown in FIG. 3. In this positionpassageway135 communicates with passageway 147, which in turn is open to chamber Eand chamber B. Plunger 140 can he forced downwardly within the plungerseat to provide communication between passageways 135 .138, and by meansof O-ring 144 cut 011 communication between passageways 135 and 147.

The portion of plunger 140 extending from reset pilot valve 130 extendsthrough a bifurcated yoke 148 'of arod 149, which yokecan engageshoulders 150 and 151 of the plunger. The rod 149 is pivotally securedto the reset pilot housing at its lower end 152. An arm 153 of the rodis connected to the upper end of a spring 154, the lowerend of which isconnected to :a lever 155. upper .end of the lever 155 ispivotallyconnected at 156 to the wall of the reset pilot housing. Thelowerportion of the lever 155 is constantly urged-toward diaphragmhousing 120 by spring 157,,the opposite end of which abuts adjustablespring plate 158 within spring housing ,15 9 secured to reset pilothousing 121.

tion'shown in FIG. 3,- should the flow line pressure in chamber A'increase sufficiently, diaphragm 124 will flex to the right, forcingplunger 160 against lever 155. Lever 155 now pivots about 156 andagainst spring 157, and

:rnoves thelower end of spring 154 to the right of the upper endthereof. When the line between the ends .-of spring 154 intersectsthelongitudinal axis of the red 149 (i.e., when the lower end of spring154 is to the rightof point 152), yoke 148 will engage shoulder 151 andforce plunger 140downwar'dly to the right, and the passageways 135 and138 of pilot valve 130 will be placed in communication with one another.

Should the flow'line pressure in'diaphragm chamber F decreasesufliciently, spring 157 will force the lower end of the lever 155 tothe left, thus repositioning the lower end of spring 154 to the left ofthe longitudinal axis of the rod 149, thus forcing yoke 148 againstshoulder 150 of the plunger and moving it back to the positionillustrated in FIG. 3. This is due, of course, to the moment created onlever 155 by spring 157 being larger than that created thereon bydiaphragm 124 through the plunger 160.

Prior to placing the manifold into operation, there is no flow in flowline 12, due to the fact that safety valve has closed the tubing string14. To place the manifold in operation, the following operations areeffected. First, after the pronged member 115 is threadedly connected togate valve 63 and sealed thereto to prevent a decrease in pressurethrough nipple 61, the gate valve is opened. Then, the pronged member115 is forced against the piston hold down 106 sufliciently to forcepiston 103 and plunger 112 inwardly to seat ball 113 against the seatassembly 87, 88 and 89. This arrangement is maintained. Secondly, thehydraulic system is charged to the desired operating pressure throughthe valve 22 from the pressure source 23. The hydraulic system consistsof safety valve 15 and conduit '17, the four-way fitting 19, connector52, conduits 101 and 99, passageway 94, and the accumulator 93. When thesafety valve 15 has been opened by this hydraulic fluid, and thehydraulic system is charged to the desired pressure, valve 22 is closedand the pressure source may be disconnected therefrom. The fluid withinthe hydraulic system is now the fluid source for the actuation of valve15 to open position. Now that the safety valve 15 is open, fluid in theflow line 12 enters chamber A through connector 59, and pressure buildsup in end-sub passageway 123 and chamber F in the diaphragm housing 120(FIG. 3). When the pressure in chamber F reaches the desired magnitude,as previously determined when spring 157 was set, the automatic resetpilot operates, as previously explained, to provide communicationbetween passageways 135 and 138. Now, flow line pressure in chamber Abuilds up in piston chamber D (through conduits 137, 131 and 82) to thepoint where the force exerted on ball 113 through plunger 112 and piston103 is greater than the force exerted on the ball by the hydraulic fluidwithin passageway 94. When such is the case, the plunger 115 isretracted, the gate valve is closed,

the pronged tool is removed from the gate valve, and

the piston hold down 106 is forced by pressure in chamber D to theposition shown in FIG. 2B. The manifold 10 is now in operation.

With the tamper proof manifold in the operating position as justdescribed, the safety valve will be closed upon the occurrence of eitherof two conditions: first, the reduction of hydraulic fluid pressurebelow a predetermined inagnitude; and, secondly, the reduction of flowline pressure in chamber A in the manifold below a predeterminedmagnitude proportional to the hydraulic fluid pressure. The results ofthe occurrence of either of these two conditions is next described.

Should the hydraulic pressure within the valve 15 or the conduit 17 bereduced below the predetermined magnitude, either by its being bled offat valve 22 or by rupture of the line 17, the valve 15 will be closed bythe spring 31 therein. The same result will be obtained in the eventthat either the conduit 99 or accumulator 93 develops a leak, due to thefact that these elements are 'valve passages 135 and 138, and conduits131 and 82;

the plunger 140 of the pilot valve 130 being in a position to the rightopposite to that shown in FIG. 3. Thus is the pressure in chamber Dacting on the relatively large area of piston 103) being greater thanthe force exerted by the hydraulic fluid pressure on the exposed surfaceof the ball 113, the ball prevents the loss of hydraulic fluid into thechamber B (at atmospheric pres sure), and thus prevents the safety valve15 from closing. However, should either the outer casing 35, flow line12, or conduit 16 be ruptured or opened in any manner, or should gatevalve 63 be opened, the pressure in chamber A will thereby be reduced toa predetermined level, and the safety valve 15 will be closed as aresult of the following. First, the pressure in diaphragm chamber F willbe reduced to the same pressure as in chamber A and spring 157 will moveplunger 140 to the position shown in FIG. 3. Secondly, the pressure inpiston chamber D -will be bled to atmosphere through the now fluidlyconnected conduits 82 and 131, and passages 135 and 147 of the pilotvalve 130. Thirdly, the hydraulic pressure in passageway 94, beinggreater than that now in piston chamber D, will force ball 113, plunger112, and piston 103 to the right, thus permitting the hydraulic fluidpressure to bleed into chamber B which is at atmosipheric pressure.Without the hydraulic fluid pressure's maintaining it open, the safetyvalve 15 closes.

Although this invention has been described for a well having a singletubing string, it is apparent that a system such as that shown in FIG. 1can be provided for each tubing string of a multiple tubing string well,which systems can be made to operate singly, or in any combination'desired.

It should be noted that chambers D and A are not directly connected toone another, but rather that the pilot valve 130 is connectedtherebetween. If chambers D and A were directly connected, the closingof passage 94 by ball 113 would be governed by two variables: the

hydraulic pressure in passageway 94, and the line pressure in chamber D.This, of course, precludes designing piston 103 so that it will releaseball 113 at any specific chamber D pressure. However, by the use of thepilot valve 130, the closing of the ball valve will depend upon only onevariable; namely, the pressure in chamber A, and upon one fixedconstant, the spring force of spring 157. In normal practice, thehydraulic system is over-charge to compensate for normal leakage and toextend maintenance intervals. For example, if the safety valve 15 is setto close when the hydraulic pressure is below 500 p.s.i., the hydraulicsystem may be charged to 1000 or with the force exerted on ball 113 byplunger 112 (which even 2000 p.s.i. Now, if piston 103 is designed tokeep the safety valve 15 open when the chamber D and hydraulic pressuresare 200 and 2000 p.s.i., respectively, and if over a period of time thehydraulic pressure drops to 500 p.s.i., the chamber D pressure can dropconsiderably (say, to p.s.i.) without closing valve 15; this situation(where line pressure drops due to a partial rupture of line 12) couldoccur in wells which have a very high producing rate. This will notoccur when the automatic reset pilot is used because spring 157 isdesigned to release the hydraulic pressure when line pressure (chambersA and D) drops to a predetermined desired level; hence, ball 113 iscontrolled independently of hydraulic pressure, and the manifold is madesensitive to any desired change in flow line pressure.

Another example of the use of the pilot valve is to assume that thehydraulic system and chamber D (flow line) pressures are 2000 and 200p.s.i., respectively, and that valve 15 will close when the hydraulicpressure drops below 500 p.s.i. and the chambers A and D were directlyconnected. A hole might be made in flow line 12, which would besufiicient to lower the pressure therein to p.s.i. This would permitball 113 tobecome unseated and the hydraulic fluid pressure to drop to,say, 1500 p.s.i., whereupon ball 113 would be reseated. In this case,the safety valve 15 would not close and a large quantity of oil could belost. This would not occur with aaaaozc 7 fli'i set: pilot in usebecause it could'be set to detect very gets-11 flow linepressurechanges, Itis important to obe that chamber D is "vented toatmospheric pressure as soon as the reset pilot detects a change in flowline pressiife; This completely vents the hydraulic system'and snows thesafety valve 15 to close completely.

It is to be realized that the embodiment of the inventiop; herewithshown and described, to be taken as a preferred embodiment of the same,and that various eas ges in the shape, size and arrangement of parts maybe resorted to without departing from the spirit of the invention or thescope of the attached claims. 7 l 'l-laving thus described ourinvention, what we claim ass desire to secure by Letters Patent is:

1; Apparatus of the character described for use in a y'stem having awell tubing string with a subsurfacesafety agar off valve made uptherein, a fluid pressure operated ate: for holding said safety shut onvalve open, a cc of fluid under pressure connected to said actuator a da surface flow line connected to said tubing, said ape t'us comprising:an outer casing, an inner casing dis- ,csmnerywanm said outer casing soas to form an outer chamber between said casings and an inner chamberwithin said inner casing, passage means communicatrag said inner chamberthrough said outer casing to atmosph re, a first conduit communicatingwith said outer amber and adapted to be connected to said flow line, a scond conduit communicating with said inner chamber adapted to beconnected to said source of fluid under pressure, a relief valveconnected in said second conduit, a'ndgin'eans responsive topressurewithin said outer chamr for opening said relief valve upon the presence'of a predetermined 10w pressure in said outer cha mb'en Appar'atus ofthe character described for use in a s emhaving a well tubing stringwith a subsurface safety shut ofi valve made up therein, a fluidpressure operated a at'o'ifor holding said safety shut 01f valve open, ag cc of fluid under pressure connected "to said actuator an'd a surfaceflow line connected to said tubing, said apparents comprising: an outercasing, an inner casing'discompletely within said outer casing so as 'toform outer chamber between said casings 'and an inner chamber withinsaid inner casing, passage means comnlunicating -said inner chamberthrough'said outer casg "to atmosphere, a first conduit communicatingwith E s d outer chamber and adapted to be connectedto said :"flo'wline, a second conduit having one end thereof com- -i'n'unic'ating withsaid inner chamber and adaptedto have its other end connected to saidsource of fluid under pres- ;sure, a relief valve disposed within 'said'inner chamber and connected to said second conduit, and rnea'ns response '0 pressure within said outer chamber for' opening lief valve'upon thepresence of'a predetermineddow sure in said outer'chainber. V i

" *3. Apparatus as set forth'in 'claim -2 further including a i ariablecapacity enclosed fluid pressure reservoirdisposed'within said innerchamber, means fluidly connecting said reservoir to said second conduitbetween said relief valve therein and said other end thereof.

4. Apparatus of the character described for use in a system having a'well tubing string with a subsurface safety shut-off valve made uptherein, a fluid pressure operated actuator for holding said safetyshutoff valve open, a cc of fluid unde'r'press'ure connected'to'sai'dactuator fandasurfa'ce flow line connected to said tubing,sai'd"apparatus comprising an outer casing, an inner "casingdispose'dcompletely Within-said outer casing so as to form outer chamberbetween said casings and an innerchamber-within said innercasinggpassage' means communicatu'ngsaid inner 'chamberthrough saidouter casingto at1 nosfphe're, a first conduit communicating with'fsa'idouter {chamber and adapted to be connected to said -flow li ne, 5asecond-conduit communicating with said inner chamiber and adapted t'obe'connected'to said source' of fluid ''urider"pressure, a relief valvein said second conduit for venting said second conduit to saidinnerchamber, a fluid pressure operated valve'actuator means operativelyassociated with said relief valve for holding said relief valve closedupon the existence of a predetermined high fluid pressure actingupon'said actuator means and for opening said relief valve when thefluid pressure acting thereon drops below said predetermined highpressure, means communicating the pressure in said outer chamber withsaid fluid pressure operated valve actuated means, and means fluidlyconnecting said actuator means with said outer chamber.

5. Apparatus of the character described for use in a system having awell tubing string with a subsurface safety shut oif valvemade uptherein, avfluid pressure operated actuator for holding said safety shutoff valve open, a source of fluid under pressure connected to saidactuator and a surface flow line connected to said tubing, saidapparatus comprising: an outer casing, an inner casing disposedcompletely within said outer casing so as to form an outer chamberbetween said casings and an inner chamber withinsaid inner casing,passage means communicating said inner chamber through said outer casingto atmosphere, a first conduit communicating with,

said outer chamber and adapted to be connected to said flow line, asecond conduit having one end thereof communicating with said innerchamber and adapted to have its other end connected to said source offluid under pressure, a relief valve in said second conduit for ventingsaid second conduit :to said inner chamber, a pressure operated reliefvalve actuator operatively associated with said relief valve for holdingsaid relief valve closed, a pilot valve having a movable valve membertherein, a first fluid connection from said pilot valve to said 1reliefvalve actuator, second and third connections from said 1pilot valve tosaid outer and inner chambers respectively, said pilot valve memberhaving a first position wherein said first and second connections are influid communication and a second position wherein said ,first :and thirdconnections .are in fluid communication, and means responsiveto-pressure within said outer chamber for holding said pilot valvemember in its first position when :the outer :chamber pressure is abovea made termined value and formoving said pilot valve member to itssecond position when said outer chamber pressure is below saidpredetermined value.

6. Apparatus as setforth in claim 5 further including 'a variablecapacity enclosed fluid pressure reservoir disposed within said innerchambenlneans fluidly connecting said reservoirto said second'conduitbetweensaid relief valve therein and said other end'thereof. 7.Apparatus of the character described ,for use in a .system having a welltubing string with ,a subsurface safety shut off valve made up :therein,a fluid pressure operated actuator for holding said safetyshut olf valve'open, a source of fluid under pressure "connected to said actuator anda surface flow line connected to said tubing, said apparatus comprising:an' outer casing, an'inner casing disposed completely within said'outercasing so as to form an outer chamber between said casingsand aninner chamber within said inner casing, passage means communicating saidinner chamber through said outer casing to atmosphere, a first conduitcommunicating with said outer chamber andadapted-to be connected to said-flow line, a second conduit having one end thereof comlmunicating withsaid inner chamber and adapted to have vits other end connected to saidsource of fluid under pressure, said second conduit having a valve seattherein facing downstream into said inner chamber, a relief valve memberseatable upon said valvcseat to prevent fluid flow therepast, a'holddown member engageable with said valve memher,a'pressi1re operated'valveactuator operatively associated with said hold down member and operabletoforce saidhold down member against said relief valve member to holdsaid valve member against said valve seat, means fluidly communicatingsaid valve operator with said outer chamber, a pilot valve having amovable valve member therein, a first fluid connection from said pilotvalve to said relief valve actuator, second and third connections fromsaid pilot valve to said outer and inner chambers respectively, saidpilot valve member having a first position wherein said first and secondconnections are in fluid communication and a second position whereinsaid first and third connections are in fluid communication, and meansresponsive to pressure within said outer chamber for holding said pilotvalve member in its first position when the outer chamber pressure isabove a predetermined value and for moving said pilot valve member toits second position when said outer chamber pressure is below saidpredetermined value.

8. Apparatus as set forth in claim 7 further including a variablecapacity enclosed fluid pressure reservoir disposed within said innerchamber, means fluidly connecting said reservoir to said second conduitbetween said valve seat therein and said other end thereof.

9. Apparatus as set forth in claim 7 wherein said pressure operatedvalve actuator comprises a piston chamber and a piston axially movabletherein, said hold down member being movable by said piston towards saidvalve seat upon admission of fluid under pressure into said pistonchamber. a

10. Apparatus as set forth in claim 9 further including means forming aclosable opening through said outer casing, and means including apronged member sealably insertable through said opening to force saidrelief valve member against said valve seat.

References Cited in the file of this patent UNITED STATES PATENTS2,780,290 Natho Feb. 5, 1957 2,785,755 En Dean Mar. 19, 1957 FOREIGNPATENTS 774,783 Great Britain Mar. 7, 1957

